Roller locked

Notable examples of firearms using this method are the MG 42 general-purpose machine gun and the CZ 52 semi-automatic pistol.

The origin of the roller-locking is debated:[1] even though the general principle of utilizing "ball bearing parts" under radial pressure "for preventing uncoupling of the coupling members" was known no later than 1910s,[2] it was apparently not used in firearms until 1930s.

For that the bolt head ends in an angled/oblique wedge to smoothly move the rollers outwards into their lockup position.

When the gun is fired, the barrel, slide, and locking piece (right side of picture) will move backward a short distance, while the locking piece will be stopped by a tab on the frame, shown on the left with a stick pointing out the mating surface.

Momentum will carry the slide back against the pressure of the recoil spring where extraction and feeding of a fresh cartridge happen similarly to other designs.